1. Field of the Invention
The present invention is generally related to a valve and, more specifically, to a solenoid valve that is provided with a sound dampening feature which comprises a resilient member attached to a moveable plunger which dampens the impact between a moveable plunger and a fixed stop member and, in certain cases, prevents direct contact between these components.
2. Description of the Prior Art
Many different types of solenoid valves are well known to those skilled in the art. In a typical application of a solenoid valve, a metal plunger is slidably disposed along a central axis within a central cavity of a solenoid coil. When the solenoid coil is energized, the magnetic flux generated by the coil caused the plunger to move axially along the centerline of the solenoid coil. Typically, the plunger is provided with a resilient seal member that moves into blocking association with a fluid port. In some applications of solenoid valves, the plunger is provided with a second resilient seal member that moves into blocking association with another fluid port in alternating synchronization with the first resilient seal. In other words, when the plunger is caused to move in a first direction, a first seal blocks a first fluid conduit and when the plunger is caused to move in the opposite direction, a second seal blocks a second fluid conduit. However, it should clearly understood that many solenoid valves are used in conjunction with a single resilient seal and a single fluid conduit.
U.S. Pat. No. 5,127,627, which issued to Domke on Jul. 7, 1992, discloses a solenoid valve that comprises a threaded sleeve assembly. Although the present invention is not directly related to the threaded sleeve assembly structure, the Domke patent describes the operation of solenoid valves and discusses the type of structure in which the present invention is intended to operate. U.S. Pat. No. 5,127,627 is expressly incorporated by reference in this application.
The Domke patent discloses an improved solenoid valve wherein the improvement is a modified sleeve assembly. The sleeve assembly is a tubular section having an enlarged first end integrally formed with the remainder of the tubular section and having a second end. The enlarged end is formed with external threads which mate with threads of a cup-like recess in the body of the solenoid valve. The tubular section is a nonmagnetic material which is screwed into the cup-like recess of the body. The enlarged first end further has a gasket seal for compressing a gasket between the cup-like recess of the body and the sleeve member. A stop of magnetic material is welded to the section end of the tubular section forming a seal. A flux plate comprising a magnetic material is located about the sleeve assembly between an electrical coil and the body.
One problem that is often encountered during the operation of solenoid valves is the sound of the impact between a plunger and a mechanical stop when the plunger is moved toward the stop by the action of a solenoid coil. This is particularly troublesome in double acting valves, but could be experienced in certain designs of single acting valves. As will be described in greater detail below, the plunger can move into momentary contact with the stop member during the deformation of the resilient valve seal upon initial impact with the fluid conduit which it is intended to block. This momentary impact can cause a clicking sound. It would therefore be beneficial if a valve could be provided which eliminates or significantly reduces the clicking sound without adversely affecting the flow of fluid through the valve.